July 13, 2009

Amphibians Synchronize Mating Under The Full Moon

Researchers have found that the mating activity of amphibians is synchronized by the full Moon.

The fascinating fact that frogs, toads and newts across the globe seem to enjoy mating by moonlight has never before been noticed.

It appears that in order to make sure that a sufficient number of males and females join up at the same time, they use the lunar cycle to co-ordinate their gatherings.

This proves to be an ingenious tactic. By taking advantage of this very specific time, the animals are able to maximize success in procreation and reduce their odds of being eaten by predators.

A full detailed report of this discovery has been published in the journal Animal Behavior.

It all started in 2005 when biologist Rachel Grant of the Open University was studying salamanders near a lake in central Italy for her PhD. That is when she noticed toads all over the road, under a full Moon.

"Although this might have been a coincidence, the following month I went along the same route every day at dusk and found that the numbers of toads on the road increased as the Moon waxed to a peak at full Moon and then declined again," she says.

After reviewing the scientific literature and finding little to no mention of any similar records, Grant returned to the same site for two subsequent years to again survey the amphibians more carefully.

Grant was then able to collate her data with a 10-year analysis of the mating habits of frogs and toads at a pond near Oxford, UK, collected by her supervisor Tim Halliday as well as with data on toads and newts in Wales collected by her colleague Elizabeth Chadwick from Cardiff University, UK.

"We analyzed the data, and found a lunar effect at all three sites," Grant says.

The common toad (Bufo bufo), for example, would arrive at all its breeding spots, and then mate and spawn under the full Moon. Also, the common frog (Rana temporaria) reportedly spawns around the time of the full Moon.

"Newts also seem to be affected by the lunar cycle but the results are less clear," says Grant.

Newt (Lissotriton vulgaris, L. helveticus and Triturus cristatus) arrivals are at their highest during both the full and new moons.

However, "newts appear to avoid arriving at the breeding site when the Moon is in its third quarter. This could be because the Earth's magnetic field is highest at that time. More research is needed to clarify this," said Grant.

After looking at historical data collected in Java on the Javanese toad (Bufo melanostictus), the researchers found that their mating patterns also correlate with the lunar cycle, with females ovulating on or near the full Moon.

"We now have evidence of lunar cycles affecting amphibians in widespread locations. We definitely think that Moon phase has been an overlooked factor in most studies of amphibian reproductive timing," says Grant.

"We think this may be a worldwide phenomenon. However, differences between species in ecology and reproductive strategy may mean that not all amphibians are affected in the same way. This is something we would like to investigate further."

Now, Grant and her colleagues are hoping to develop a statistical model that would take into account weather factors and environmental variables such as geomagnetism along with the lunar cycle.

The ability to accurately predict the movements of amphibians is a crucial part of conservation, according to Grant. If mating times were predicted, they could close roads at that given time in order to prevent cars killing thousands of the frogs and toads mating there.

"Given the current global crisis among amphibian populations, further understanding of [their] breeding behavior is extremely important," she says.